Development of indices of biotic integrity for high-gradient wadeable rivers and headwater streams in New Jersey

The New Jersey Bureau of Freshwater and Biological Monitoring (BFBM) has been conducting Fish Index of Biotic Integrity (FIBI) monitoring on rivers and streams (with drainage area >12.95 km2) in the Northern part of the state since 2000 using Karr's original IBI format with several regional modifications. In an effort to increase the overall performance of the IBI and to assess smaller headwater streams, a new design and approach to metric development was evaluated on approximately 230 high gradient streams. This design, developed by Thomas Whittier and Robert Hughes, has been implemented for numerous Western U.S. studies, as well as the Connecticut multi-metric indices (MMI). Analysis resulted in two distinct stream classes; a coldwater community (Headwaters IBI) with drainage area <10.36 km2 consisting of brook trout, sensitive salamanders, and native crayfish and cool/warmwater fish communities (Northern FIBI) with drainage area >10.36 km2. Over 140 metrics from ten ecological classes were tested for signal to noise, range, responsiveness, and redundancy. A total of eight metrics representing seven ecological classes were selected for the Northern FIBI and six metrics representing five ecological classes were selected for the Headwaters IBI. These two indices provide the Bureau with an effective and sensitive biological tool to monitor and assess all non-tidal, wadeable streams in the Piedmont, Highlands, and Ridge and Valley physiographic ecoregions.